1 /*
2 ** Copyright 2016, The Android Open Source Project
3 **
4 ** Licensed under the Apache License, Version 2.0 (the "License");
5 ** you may not use this file except in compliance with the License.
6 ** You may obtain a copy of the License at
7 **
8 ** http://www.apache.org/licenses/LICENSE-2.0
9 **
10 ** Unless required by applicable law or agreed to in writing, software
11 ** distributed under the License is distributed on an "AS IS" BASIS,
12 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 ** See the License for the specific language governing permissions and
14 ** limitations under the License.
15 */
16
17 #include <fcntl.h>
18 #include <linux/unistd.h>
19 #include <sys/mount.h>
20 #include <sys/wait.h>
21
22 #include <sstream>
23
24 #include <android-base/logging.h>
25 #include <android-base/macros.h>
26 #include <android-base/stringprintf.h>
27
28 #include "installd_constants.h"
29 #include "otapreopt_utils.h"
30
31 #ifndef LOG_TAG
32 #define LOG_TAG "otapreopt"
33 #endif
34
35 using android::base::StringPrintf;
36
37 namespace android {
38 namespace installd {
39
CloseDescriptor(int fd)40 static void CloseDescriptor(int fd) {
41 if (fd >= 0) {
42 int result = close(fd);
43 UNUSED(result); // Ignore result. Printing to logcat will open a new descriptor
44 // that we do *not* want.
45 }
46 }
47
CloseDescriptor(const char * descriptor_string)48 static void CloseDescriptor(const char* descriptor_string) {
49 int fd = -1;
50 std::istringstream stream(descriptor_string);
51 stream >> fd;
52 if (!stream.fail()) {
53 CloseDescriptor(fd);
54 }
55 }
56
57 // Entry for otapreopt_chroot. Expected parameters are:
58 // [cmd] [status-fd] [target-slot] "dexopt" [dexopt-params]
59 // The file descriptor denoted by status-fd will be closed. The rest of the parameters will
60 // be passed on to otapreopt in the chroot.
otapreopt_chroot(const int argc,char ** arg)61 static int otapreopt_chroot(const int argc, char **arg) {
62 // Validate arguments
63 // We need the command, status channel and target slot, at a minimum.
64 if(argc < 3) {
65 PLOG(ERROR) << "Not enough arguments.";
66 exit(208);
67 }
68 // Close all file descriptors. They are coming from the caller, we do not want to pass them
69 // on across our fork/exec into a different domain.
70 // 1) Default descriptors.
71 CloseDescriptor(STDIN_FILENO);
72 CloseDescriptor(STDOUT_FILENO);
73 CloseDescriptor(STDERR_FILENO);
74 // 2) The status channel.
75 CloseDescriptor(arg[1]);
76
77 // We need to run the otapreopt tool from the postinstall partition. As such, set up a
78 // mount namespace and change root.
79
80 // Create our own mount namespace.
81 if (unshare(CLONE_NEWNS) != 0) {
82 PLOG(ERROR) << "Failed to unshare() for otapreopt.";
83 exit(200);
84 }
85
86 // Make postinstall private, so that our changes don't propagate.
87 if (mount("", "/postinstall", nullptr, MS_PRIVATE, nullptr) != 0) {
88 PLOG(ERROR) << "Failed to mount private.";
89 exit(201);
90 }
91
92 // Bind mount necessary directories.
93 constexpr const char* kBindMounts[] = {
94 "/data", "/dev", "/proc", "/sys"
95 };
96 for (size_t i = 0; i < arraysize(kBindMounts); ++i) {
97 std::string trg = StringPrintf("/postinstall%s", kBindMounts[i]);
98 if (mount(kBindMounts[i], trg.c_str(), nullptr, MS_BIND, nullptr) != 0) {
99 PLOG(ERROR) << "Failed to bind-mount " << kBindMounts[i];
100 exit(202);
101 }
102 }
103
104 // Try to mount the vendor partition. update_engine doesn't do this for us, but we
105 // want it for vendor APKs.
106 // Notes:
107 // 1) We pretty much guess a name here and hope to find the partition by name.
108 // It is just as complicated and brittle to scan /proc/mounts. But this requires
109 // validating the target-slot so as not to try to mount some totally random path.
110 // 2) We're in a mount namespace here, so when we die, this will be cleaned up.
111 // 3) Ignore errors. Printing anything at this stage will open a file descriptor
112 // for logging.
113 if (!ValidateTargetSlotSuffix(arg[2])) {
114 LOG(ERROR) << "Target slot suffix not legal: " << arg[2];
115 exit(207);
116 }
117 {
118 std::string vendor_partition = StringPrintf("/dev/block/by-name/vendor%s",
119 arg[2]);
120 int vendor_result = mount(vendor_partition.c_str(),
121 "/postinstall/vendor",
122 "ext4",
123 MS_RDONLY,
124 /* data */ nullptr);
125 UNUSED(vendor_result);
126 }
127
128 // Try to mount the product partition. update_engine doesn't do this for us, but we
129 // want it for product APKs. Same notes as vendor above.
130 {
131 std::string product_partition = StringPrintf("/dev/block/by-name/product%s",
132 arg[2]);
133 int product_result = mount(product_partition.c_str(),
134 "/postinstall/product",
135 "ext4",
136 MS_RDONLY,
137 /* data */ nullptr);
138 UNUSED(product_result);
139 }
140
141 // Chdir into /postinstall.
142 if (chdir("/postinstall") != 0) {
143 PLOG(ERROR) << "Unable to chdir into /postinstall.";
144 exit(203);
145 }
146
147 // Make /postinstall the root in our mount namespace.
148 if (chroot(".") != 0) {
149 PLOG(ERROR) << "Failed to chroot";
150 exit(204);
151 }
152
153 if (chdir("/") != 0) {
154 PLOG(ERROR) << "Unable to chdir into /.";
155 exit(205);
156 }
157
158 // Now go on and run otapreopt.
159
160 // Incoming: cmd + status-fd + target-slot + cmd... + null | Incoming | = argc + 1
161 // Outgoing: cmd + target-slot + cmd... + null | Outgoing | = argc
162 const char** argv = new const char*[argc];
163
164 argv[0] = "/system/bin/otapreopt";
165
166 // The first parameter is the status file descriptor, skip.
167 for (size_t i = 2; i <= static_cast<size_t>(argc); ++i) {
168 argv[i - 1] = arg[i];
169 }
170
171 execv(argv[0], static_cast<char * const *>(const_cast<char**>(argv)));
172 PLOG(ERROR) << "execv(OTAPREOPT) failed.";
173 exit(99);
174 }
175
176 } // namespace installd
177 } // namespace android
178
main(const int argc,char * argv[])179 int main(const int argc, char *argv[]) {
180 return android::installd::otapreopt_chroot(argc, argv);
181 }
182